The invention relates to a power transmission belt and more particularly to a low modulus power transmission belt.
Power transmission belts are widely used to transmit rotary power. The belt is generally installed between a driver and driven pulley, such as in the case of an accessory belt drive on a vehicle engine.
The belt comprises a tensile cord embedded in an elastomeric material. The tensile cord, or cords, are oriented parallel to a longitudinal axis in order to maximize a load carrying capability. The tensile cord is wound on a belt build in a continuous manner during fabrication.
Power transmission belts must possess sufficient tensile strength to allow a required torque, and load, to be transmitted between pulleys.
A belt having a high tensile strength also will generally have a commensurately high modulus. A belt having a high modulus will be relatively stiff and subject to higher operating temperatures. Further, installation of a prior art high modulus belt requires moveable pulleys.
A low modulus belt may be used in situations were the torque to be transmitted is relatively low. Low modulus belts are fabricated using tensile cords having little or no preload, or, are fabricated using tensile cords having a twist that allows for a predetermined elongation under load.
Representative of the art is EP 0 625 650 to Gates that discloses a low modulus belt having a tensile cord wound with a preload in a longitudinal direction.
Also representative of the art is U.S. Pat. No. 4,229,254 to Gill (1980) which discloses a belt having a reinforcing structure having two plies of cords extending in cross bias layers.
Further representative of the art is U.S. Pat. No. 6,033,331 to Winninger et al. (2000) which discloses a belt having a supporting structure such that the belt exhibits an average stress-elongation slope ranging from 12 to 20 daN/% of elongation per width centimeter.
The prior art teaches use of tensile cords that are wound in a longitudinal direction for bearing a tensile load. The art also teaches low modulus belts having a relatively moderate to high modulus.
What is needed is a low modulus belt having a multi-unit cord tensile member. What is needed is a low modulus belt having a woven fabric tensile member. What is needed is a low modulus belt having a tensile member describing a pantographic form. What is needed is a low modulus belt having a modulus less than 1,500 N/mm. The present invention meets these needs.
The primary aspect of the invention is to provide a low modulus belt having a multi-unit cord tensile member.
Another aspect of the invention is to provide a low modulus belt having a woven fabric tensile member.
Another aspect of the invention is to provide a low modulus belt having a tensile member describing a pantographic form.
Another aspect of the invention is to provide a low modulus belt having a modulus less than 1,500 N/mm.
Other aspects of the invention will be pointed out or made obvious by the following description of the invention and the accompanying drawings.
The invention comprises a low modulus power transmission belt having a multi-unit cord tensile member. The belt also comprises a low modulus elastomeric body. A multi-unit cord tensile member configuration is plied into the elastomeric body, the tensile cord members having an included angle in the range of 120xc2x0 to 180xc2x0 between each ply. The belt having an elastic modulus of less than 1,500 N/mm and having an elongation of approximately 6.8% over a load range of approximately 0-350 newtons.